High Transmission Coefficient Research Articles

Characterisation of chemical bath deposited CdS thin films on different substrates using electrolyte contacts

Aqueous electrolyte contacts have been used to characterize CdS thin films grown using chemical bath deposition (CBD) on 4 different fluorine-doped tin oxide (FTO) coated conducting glass substrates (identified by the supplier Pilkington Group Limited as TEC-15, TEC-7, NSG low-E, and NSG Solar). The porosity of CdS layers prepared on different substrates was evaluated by voltammetry using the oxidation of hexacyanoferrate (II) to probe residual electrochemical activity arising from the underlying conducting substrate. Using a simple model, it can be concluded that thin films deposited on NSG substrates at 85 °C are probably nanoporous with a porosity of up to ~ 20% of the coverage of the CdS surface. The porosity appears to depend on the nature of the substrate rather than the physical parameters of the deposition. In the case of non-porous films deposited on TEC substrates, analysis of the impedance gave values of the space charge capacitance from which the doping density and flat band potential were derived. The doping densities for CdS were found to be in the order of 10 17 cm −3–10 20 cm −3 depending on the substrate. The transmission spectra, recorded in the UV–visible range, reveal a relatively high transmission coefficient in the obtained films. The transmittance data further indicate that the optical band gap is closely related to the deposition conditions. Micro-Raman analysis showed structural similarity and differences between porous and non-porous thin films.

The Impact of On-Wafer Calibration Method on the Measured Results of Coplanar Waveguide Circuits

This paper compares four commonly used on-wafer calibration methods including multiline thru-reflect-line (TRL), line-reflect-reflect-match, line-reflect-match, and short-open-load- thru, for three diverse coplanar waveguide (CPW) circuits. The magnitudes and phases of S 11 and S 21 of the CPW circuits are compared to quantify how the specific calibration method influences measured scattering parameters. Special care is taken to ensure that the measured scattering parameters are normalized to the same reference impedance and reference plane for accurate comparison. The measured results are compared with full-wave simulations to provide additional assessment of accuracy. A method to de-embed the discontinuity of the CPW at the probe tip and the CPW of the test structures is presented. The effect of probe-to-device-under-test discontinuity is effectively modeled by one- or two- section of shunt capacitor and series inductor. The results show that the multiline TRL calibration method provides the highest transmission coefficient repeatability on not well-matched circuits and highest accuracy on the three circuits in this paper up to 40 GHz.

Growth and physical properties of CdS thin films prepared by chemical bath deposition

This work deals with the preparation of cadmium sulfide (CdS) thin films by chemical bath deposition. The influence of the solution temperature is investigated in this study. We suggest that activation energy of the deposition rate measurement can be a tool for determining the nature of the deposition mechanism. We found that at low solution temperature, the growth mechanism proceeds via the ion by ion process, and found the corresponding activation energy equal to 0.06 eV. However, at higher solution temperature, the film deposition became via the cluster by cluster process, the growth rate activation energy is equal to 0.48 eV. The films' structural and optical properties were studied by x-ray diffraction analysis and UV–visible spectrophotometry. Structural analysis revealed that the deposited films have a cubic structure, and the crystallite size decreases with increasing deposition temperature. The transmission spectra of the film, in the visible range, show a high transmission coefficient (70%). The transmittance data analysis indicates that the optical band gap is closely related to the solution temperature. From this analysis, a direct band gap ranging from 2.21 to 2.34 eV was deduced. From the electrical characterization we inferred that CdS films are n-type and their dark conductivities reduced with increasing bath solution temperature. From the photoconductivity measurements we concluded that films deposited at low temperatures (less than 60 °C) or high temperatures (higher than 70 °C) have good optoelectronic properties suitable for utilization as a buffer layer in thin film solar cells.

Structural and optical properties of CdS thin films grown by chemical bath deposition

Cubic cadmium sulphide (CdS) thin films with (111) preferential orientation were prepared by chemical bath deposition (CBD) technique, using the reaction between NH 4OH, CdSO 4 and CS(NH 2) 2. The films properties have been investigated as a function of bath temperature and deposition time. Structural properties of the obtained films were studied by X-ray diffraction analysis. The structural parameters such as crystallite size have been evaluated. The transmission spectra, recorded in the UV visible range reveal a relatively high transmission coefficient (70%) in the obtained films. The transmittance data analysis indicates that the optical band gap is closely related to the deposition conditions, a direct band gap ranging from 2.0 eV to 2.34 eV was deduced. The electrical characterization shows that CdS films' dark conductivities can be controlled either by the deposition time or the bath temperature.

Polarization characteristics of subwavelength aluminum wire grating in near infrared

Rigorous coupled wave analysis (RCWA) was used to investigate the polarization characteristics of subwavelength aluminum wire grating in near infrared. Upon exposure to the atmosphere, a layer of Al2O3 forms rapidly on the aluminum wires, so the effect of metal oxide layers on the polarization properties is modeled and analyzed. It is shown that subwavelength aluminum wire grating with oxide layers forming on the wires still offers excellent polarization properties. As the thickness of the oxide layer increases, the transmission coefficient increases, but the extinction ratio decreases. In addition, a magnesium fluoride (MgF2) layer was proposed to deposit between the aluminum wires and the substrate to enhance transmission coefficient. The theoretical research shows that subwavelength aluminum grid grating has high transmission coefficient and extinction ratio in near infrared, as well as uniform performance with wide variations in the angle of incidence. These features with their small size make it desirable for use in optical communication and allow more compact component designs.

Consideraciones ecomorfológicas del mecanismo de captura de presas en Xiphias gladius (Linnaeus, 1758)

El presente trabajo analiza el mecanismo de captura de presas del pez espada ( Xiphias gladius ), suponiendo un mecanismo de alimentacion RAM y una dieta de amplio espectro trofico. Se estudia la region cefalica y se describe la osteologia y miologia asociada con el mecanismo de captura de presas. Se aplica el modelo de cuatro barras para evaluar la eficiencia de la apertura bucal y un modelo biocinematico para evaluar la eficacia del cierre bucal. La mayor cantidad de estructuras del neurocraneo se encuentran desplazadas hacia la region posterior, con alto grado de calcificacion y prevalencia de articulaciones sinartricas biseladas y suturas. Se destaca la barra vertical del suspensorio que sostiene a la serie opercular y la mandibula inferior. Premaxilar y maxilar intimamente unidos sin posibilidad de movimiento relativo aunque persiste el ligamento primordial. La configuracion del sistema de palancas del musculo adductor mandibular determina el sistema biocinematico cuya eficiencia en la transmision de fuerza es del orden del 30% para el fasciculo externo (A2 +A3α), mientras que para el fasciculo interno (A3β) la eficiencia es del orden del 15%. El Coeficiente de Transmision Cinematica (K = q · r -1 ) es de 9,75; mientras que el Coeficiente de la Fuerza Transmitida (f = r · q -1 ) tiene un valor de 0,102. Se analiza y discute el diseno morfofuncional que posibilita la captura de presas que desarrollan altas velocidades, ya que el coeficiente de transmision cinematica es alto, valor coincidente con peces de habitos piscivoros.

Properties of CdS Thin Films Grown by Chemical Bath Deposition as a Function of Bath Temperature

The present work deals with the preparation and characterization of cadmium sulfur (CdS) thin films. These films are prepared by chemical bath deposition on the well cleaned glass substrates. The thickness of the samples was measured by using profilometer DEKTAK, structural and optical properties were studied by X-ray diffraction analysis, and UV-visible spectrophotometry. The optical properties of the films have been investigated as a function of temperature. The band gap energy and Urbach energy were also investigated as a function of temperature. From the transmittance data analysis the direct band gap ranges from 2.21 eV to 2.34 eV. A dependence of band gap on temperature has been observed and the possible raisons are discussed. Transmission spectra indicates a high transmission coefficient (75 %). Structural analysis revealed that the films showed cubic structure, and the crystallite size decreased at a higher deposition temperature.

Optimized focusing properties of photonic crystal slabs

We propose an optimization procedure for focusing operation in finite two dimensional photonic crystal slabs. The device consists of a triangular lattice air holes etched in a semiconductor matrix at a nanometer scale to operate at 1.55 μm. To reach simultaneously an effective refractive index equal to −1 along with a very high transmission coefficient whatever optical wave incidence, the parameters as the lattice period and/or filling factor are precisely adjusted depending on the slab thickness. The method relies on Fabry–Perot resonances engineering in the air/crystal/air cavity constituting the lens.

Growth, structural, optical and electrical study of ZnS thin films deposited by solution growth technique (SGT)

ZnS thin films have been deposited onto glass substrates at temperature 90°C by solution growth technique (SGT). The deposition parameters were optimized. Triethanolamine (TEA) was used as a complexing agent for uniform deposition of the thin films. The elemental composition of the film was confirmed by energy dispersive analysis by X-ray (EDAX) technique. Structure and surface morphology of as-deposited films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), atomic force microscopy (AFM), respectively. XRD patterns reveal that as-deposited thin films were amorphous in nature; while the obtained precipitate powder was polycrystalline in nature. SEM results revealed that deposited ZnS material has ∼120±20nm average grain size and the spherical grains are distributed over the entire glass substrate. Low surface roughness was found to be 2.7nm from AFM studies. Transmission spectra indicate a high transmission coefficient (∼75%) with direct band gap energy equal to 3.72eV while indirect band gap was found to be 3.45eV. A photoluminescence (PL) study of the ZnS at room temperature (300K) indicates a strong luminescence band at energy 2.02eV.

Self-collimating photonic crystal polarization beam splitter

We present theoretical and experimental results of a polarization splitter device that consists of a photonic crystal (PhC) slab, which exhibits a large reflection coefficient for TE and a high transmission coefficient for TM polarization. The slab is embedded in a PhC tile operating in the self-collimation mode. Embedding the polarization-discriminating slab in a PhC with identical lattice symmetry suppresses the in-plane diffraction losses at the PhC-non-PhC interface. The optimization of the PhC-non-PhC interface is thereby decoupled from the optimization of the polarizing function. Transmissions as high as 35% for TM- and 30% for TE-polarized light are reported.

Concentration of light energy within a cone with a metal coating

The spatial structure of light waves of the electric type in a cone with perfectly reflecting metal walls is theoretically analysed. The exact formulas and asymptotic expressions are derived which describe the dependences of the energy density of different components of the field inside the cone on the radial coordinate. A special attention is paid to the study of the character of the field decrease near the cone apex depending on the cone angle and the wavelength. The effects of reflection of waves from the truncated cone-free space interface are studied. The obtained results are used for measuring the transmission coefficient of a truncated cone in the optical range for a broad range of parameters, including the diameter of the output aperture of the order of 0.05 — 0.1 of the wavelength. The possibility of obtaining a high transmission coefficient of light in a truncated metallised cone is theoretically substantiated.

Variety of LaSrMnO structures induced by growth conditions and laser irradiation

Crystallographic phase transitions in perovskite-like LaSrMnO metallic oxides are studied. The transitions are induced when internal stresses generated during film synthesis (at temperatures between 450 and 730°C) vary (decrease or increase) upon subsequent irradiation by a KrF laser emitting in the UV range. As the synthesis temperature Ts grows, the rhombohedral-to-orthorhombic phase transition occurs at 650–670°C. The resistivity is shown to be either temperature-independent, ρ(T)=const, at T<Tcrit, or varies and reaches a maximum, ρ(T)=ρmax, at the Curie temperature Tc. Optical transmission spectra taken at photon energies ℏω=0.5–2.5 eV exhibit both a high (0.8–0.9) and low (0.1–0.3) transmission coefficient t, depending on the synthesis temperature. As follows from X-ray diffraction data, the laser irradiation causes a phase transition only in LaSrMnO films grown at Ts<650°C. Phases of different size scales appear: the long-range-order orthorhombic matrix and mesoscopic-range-order rhombohedral clusters are observed in the films grown at Ts=450–550°C and the rhombohedral matrix with orthorhombic clusters, in the films grown at Ts=550–650°C.

Tunneling effect in electron-stimulated desorption of Li + from LiF/Si [formula omitted

It is shown that the kinetic-energy distributions of 6Li + and 7Li + ions desorbed during electron irradiation from the system LiF/Si(1 0 0) exhibit fine structures. Their character suggests that they correspond to Li + ions emitted according to the wave packet squeezing desorption model. This observation enables us to determine the final repulsion potential active in the Li + desorption process. The oscillatory-structure onsets show that these potentials have the potential-energy barrier of a height of about 1.4 eV for the virgin LiF samples and of about 2.8 eV for LiF preirradiated with a dose of 50 μC/mm 2. For preirradiated samples the oscillatory structures are less pronounced, but for such samples relatively strong and very narrow peaks located at 2.12 eV for 6Li + and at 2.03 eV for 7Li +, respectively, can be detected. These peaks are interpreted as ions trapped in the temporary bound-states located above the vacuum level of the sample. Due to a relatively high transmission coefficient the ions can tunnel trough the temporary existing potential barrier. The lifetime of the potential barrier estimated from the peak energy width and the Heisenberg uncertainty principle is about 7 fs. Some other aspects of the dynamic lattice distortion are also discussed.

Transmissão de Radiação Ultravioleta Através do Pelame e da Epiderme de Bovinos

A transmissão de radiação ultravioleta de comprimentos de onda entre 250 e 360 nm através do pelame e da epiderme de bovinos foi determinada em laboratório, usando-se amostras de couro de animais recém-abatidos. A quantidade de radiação transmitida através do pelame depende da coloração e também das características estruturais do pelame (espessura da capa; comprimento, diâmetro, número e inclinação dos pêlos), pelas quais é definido o trajeto médio de um fóton pela massa de pêlos (L). A maior transmissão é proporcionada por pelames brancos com altos valores de L, ao passo que pelames negros em geral apresentam transmissão nula ou muito baixa. Quanto menos pigmentada a epiderme, maior a transmissão de radiação através da sua superfície. A melhor proteção é proporcionada por pelames negros com baixo valor de L sobre epiderme igualmente negra, mas em vista do aquecimento causado pela absorção de radiação térmica (em vacas Holandesas a temperatura das malhas negras atinge 44,1ºC ao mesmo tempo em que a das malhas brancas é 37,7ºC), a combinação ideal para ambientes tropicais é um pelame branco com baixo valor de L sobre epiderme negra, uma combinação dificilmente encontrada em animais de raças européias. Uma alternativa seria um pelame negro com um baixo valor de L. Animais vermelhos apresentam alta transmissão de radiação UV através da epiderme e do pelame, sendo desaconselhados para ambientes tropicais. Entretanto, foi observada uma vaca Holandesa com áreas isoladas de epiderme negra coberta com pelame branco, o que pode trazer perspectivas para uma seleção para combinações mais adequadas de epiderme e pelame em bovinos de raças européias.

Population Density and Transmission of Virus in Experimental Populations of the Western Tent Caterpillar (Lepidoptera: Lasiocampidae)

Epizootics of nuclearpolyhedrovirus (NPV) are associated with population fluctuations of western tent caterpillars, Malacosoma californicum pluviale (Dyar), in western Canada. To experimentally quantify the spread of NPV in the western tent caterpillar, we measured the transmission of NPV within and among colonies of larvae introduced to alder trees. We altered both host population size (number of larvae per colony on a tree with 4 colonies) and pathogen density (number of infected individuals introduced to 1 of 4 colonies per tree). At the scale of the tree, the transmission coefficient (proportion of new infections per initially infected caterpillar) was independent of host density, but varied with initial pathogen dose. Low doses of virus had higher transmission coefficients than high doses. Transmission of virus between colonies within trees was related to the size of the colonies and virus was more widely spread among the 4 colonies when colonies were large (256 larvae per colony). This could be attributed to variation in the development rate and mobility of caterpillars from small and large colonies. The dynamics of NPV in populations of tent caterpillars will be influenced by movement of caterpillars among colonies, but increases in the amount of virus above a threshold level will not lead directly to increased numbers of infected individuals. Individual tent caterpillar moths lay all of their eggs in a single egg mass, and in declining populations, egg masses are smaller. The slower development of small colonies arising from these smaller egg masses may delay the recovery of declining populations, restrict the spread of virus, and influence the population dynamics of tent caterpillars.

Electron Transmission through Self-Assembled Monolayers

Electron transmission through a series of self-assembled monolayer films is studied using an iterative Green's function method with absorbing boundary conditions. The nuclear-electron interactions are calculated using suitable pseudopotentials, and the Hamiltonian is evaluated using a discrete variable representation. The presence of electronegative head groups on the metal surface gives rise to much lower transmission through the layers. The presence of these headgroups also produces asymmetric transmission effects where the transmission coefficient depends on the incident direction of the electron, as observed in recent STM measurements. Longer alkane chains (up to 18 carbon atoms) are more ordered due to the self-assembly process and have higher transmission coefficients at lower electron energies. This collective effect is observable experimentally and is not a property of single molecules in which transmission probabilities decay roughly exponentially with chain length.

ZnO layers prepared by spray pyrolysis

Highly transparent undoped and indium doped ZnO thin films have been grown on glass substrates by using the spray pyrolysis process. Conditions of preparation have been optimized to get good quality and reproducible films with required properties. Polycrystalline films with an hexagonal Wurtzite-type structure were easily obtained under the optimum spraying conditions. Both of samples have shown high transmission coefficient in the visible and infrared wavelength range with sharp absorption edge around 380 nm which closely corresponds to the intrinsic band-gap of ZnO (3.2 eV). Orientation and crystallites size were remarkably modified by deposition temperature and indium doping.

農業用光透過性遮音板の研究 （第１報） 基本構造と遮音性能

In this study a noise insulating panel was developed using a natural based polymer gel sandwiched and boarded by transparent materials. In addition, a material between the boards of the noise insulating panel was selected and its application to a Welsh onion shelling machine was examined. Results of this study are as follows.1) According to the transparency, it became clear that due to the 1.0% density of Gellamgum, the decrease in the transparency was just about 10%. Furthermore, the coefficient of light transmission showed 78.3%-71.7% in the five types of densities (0.25-1.25%) of Gellamgum and effect of the density was small.2) According to the noise reduction efficiency, regarding the frequencies of the filtered noise coming through the insulating panel poured with a polymer gel, we can say that the coincidence effect at 315Hz and 3150Hz was significantly fairly reduced. By using Gellamgum, the effect and the noise at high range frequencies of 2kHz to 4kHz were fairly reduced.From the measurements conducted, it was clear that Cgllemgum having a noise reduction efficiency, has a high light transmission coefficient. From the economic view point, the ease of handling and manufacturing, Gellamgum gel with 1% density was suitable and it was decided to be used as a stuffing material for the boards of the noise insulating panel.3) Using the noise insulating panel, a soundproof cover for the Welsh onion shelling was constructed and was examined in order to reduce the noise.Results of the frequency analysis showed that the noise coming from high frequency vibration of Welsh onion shells at frequency of 2.5kHz was reduced by 16.2dB. Moreover, it became clear that using the soundproof cover with high noise reduction efficiency, the transparency was the highest at 75%, and the soundproof cover was able to provide an excellent working environment relating to sense of hearing as well as sense of sight. Gellamgum widely used in food industry, acrylic plate and glue sold at market were used as basic materials for the soundproof cover which could be constructed easily. Therefore, every farmer having a small budget could possibly fabricate a soundproof cover which is pretty easy to use.

Composite systems for display applications from cellulose elastomers and nematic liquid crystals

Composite systems made from cellulose derivatives solid films impregnated by a nematic liquid crystal can be used as electro-optical devices [H.V. Craighead, J. Cheng, S. Hackwood, Appl. Phys. Lett., 40 (1982) 22; M.H. Godinho, J.L. Figueirinhas, A.F. Martins, Liquid Cryst., 20(3) (1996) 373]. The electro-optical behavior of such cells depends on the nature of the cellulose derivative used, the nematic liquid crystal, the preparation conditions of the cells and of the cellulosic films, and the rugosity of the films' surface [M.H. Godinho, J.L. Figueirinhas, A.F. Martins, Liquid Cryst., 20(3) (1996) 373; M.H. Godinho, A.F. Martins, A. Almeida, J.L. Figueirinhas, 16th International Liquid Crystal Conference, Kent USA, June 24–28, 1996]. In this work we study the influence of preparation techniques, number of polymer layers (1–3 layers eac9 μm thick), thickness of the liquid crystal layer (8– μm) and ageing (9 months), upon the electro-optical response of the cells. The cells used in this work were shown to exhibit high transmission coefficients (up to 82%) in the activated state and high contrast (up to 266). They also show good temporal stability and the cells' optical behaviour is strongly dependent on the number of films' layers.

The reactive flux method applied to complex isomerization reactions: Using the unstable normal mode as a reaction coordinate

A basic problem when calculating reaction rates using the reactive flux method is the introduction of a reaction coordinate. In this paper we show that it is advantageous to define a reaction coordinate by means of the unstable normal mode of the saddle point of the potential energy surface. This particular choice is made since it yields a high transmission function. Moreover, the reaction coordinate is calculated via a rapidly converging algorithm, and its derivative, which is needed in constrained runs, is calculated analytically. Calculations on the transmission coefficient of the isomerization of n-butane are in good agreement with results published by others. Runs with an isomerizing calix[4]arene in vacuo produce a very high transmission coefficient, as is the purpose of the reaction coordinate. The same molecule is also studied in chloroform.